Methods and systems disclosed herein relate generally to de-orbiting objects in outer space, and in particular, de-orbiting debris from the highly populated sun synchronous orbit region by injecting micron scale dust grains in this region. Small objects, for example, but not limited to, space debris, can be difficult to track individually and remove, thus making small objects possibly dangerous to other orbiting objects. Referring now to FIG. 1, orbital debris with characteristic size of 10-1000 cm are shown to be far less numerous than orbital debris with characteristic size smaller than 10 cm. The small object population is localized at an altitude around 1000 km and between 50-100 degrees in inclination angle. The approximate lifetime of these small objects with perigee of 800 km or less and having a ballistic coefficient of three or less is approximately 25 years or less due to natural atmospheric drag. In an effort to reduce future accumulation of orbital debris, U.S. Government guidelines specify that space objects are to be de-orbited within 25 years of mission completion. (see “Process for Limiting Orbital Debris”, NASA-STD 8719.14, published in 2007). Thus, what is needed is to relocate the orbits of the small object populations that peak around 1000 km altitude, that have lifetimes of centuries, to below an altitude so that they can be naturally de-orbited within 25 years or less. Space objects such as debris can be broadly classified into two categories: (i) large objects with dimension larger than 10 cm and (ii) small objects with dimension smaller than 10 cm. The smaller debris can be more numerous and can be difficult to detect and can be impossible to individually track. These characteristics can make them more dangerous than the fewer larger objects that can be tracked and hence avoided. In addition, there are several solutions for addressing larger objects, for example, DARPA/NRL's FREND device that can remove large objects from useful orbits and place them in graveyard orbits. However, damage from centimeter to millimeter size objects can be dangerous.
Referring now to FIG. 2A, a 4 mm diameter crater on the windshield of the Space Shuttle was created by impact of 0.2 mm paint chip. Referring now to FIG. 2B, a hole on an antenna of the Hubble space telescope was created by the impact of an object of less than 1 cm. These collisions could create vulnerability in space operations that could become more severe in the future. What is needed is a small object removal system and method that can address this vulnerability and that could ensure uninterrupted access to the near-earth space.
Referring now to FIG. 3A, an exemplary tracked object population is shown to be localized within about 50° of inclination angle. Referring now to FIG. 3B, objects in sun synchronous orbits, where most of the orbital debris is located, have nearly circular orbits. The larger trackable debris peaks around 800 km altitude. Referring now to FIG. 4, the smaller objects, although difficult to track individually, can be tracked statistically and the resulting distribution is roughly similar to the tracked objects shown in FIG. 3B but peaks at higher (˜1000 km) altitude. Referring now to FIG. 5, the orbital lifetimes of objects as a function of their ballistic coefficient (B), defined as the mass to area ratio, are shown. Objects with B˜3 peak around 1000 km and their lifetimes become 25 years or less below 900 km. Above 900 km the lifetimes can become centuries. Therefore, the task of small object removal is essentially to reduce the object orbit height from around 1100 km to below 900 km and then let nature take its course. For faster removal in less than 25 years the debris altitude may be lowered farther. There are about 900 active satellites and about 19,000 earth-orbiting cataloged objects larger than 10 cm. However, there are countless smaller objects that can be difficult to track individually. Unintentional (collision or explosion) or intentional fragmentation of satellites can increase the object population significantly. For example, the 2007 Chinese Anti-Satellite test generated 2400 large objects and countless smaller ones in the very popular sun synchronous orbit at about 865 km altitude. A similar increase of object population also resulted from the 2009 collision of an Iridium satellite with a spent Russian satellite. The object population is expected to rise substantially as more and more nations become space faring.
What are needed are a system and method to induce rapid reentry of orbital debris.